1. Field of the Invention
The present invention relates to a toner that can suitably be used in an image forming apparatus of an electrophotographic system.
2. Description of the Related Art
In an image forming apparatus utilizing an electrophotographic system, an image is formed by passing through, for examples, a charging step, an exposure step, a development step, a transfer step, a cleaning step, a charge removing step and a fixing step. A surface of a photoreceptor rotatably driven is uniformly charged by a charging apparatus in the charging step, and the charged surface of the photoreceptor is irradiated with laser light by an exposure apparatus in the exposure step.
Thus, an electrostatic latent image is formed on the surface of the photoreceptor. The electrostatic latent image on the surface of the photoreceptor is developed using a developer by a developing device in the development step, whereby a toner image is formed on the surface of the photoreceptor, and the toner image on the surface of the photoreceptor is transferred to a transfer material by a transfer apparatus in the transfer step.
The toner image is then heated by a fixing apparatus in the fixing step, whereby the toner image is fixed to the transfer material. A transfer residual toner remaining on the surface of the photoreceptor after image formation operation is removed by a cleaning apparatus in the cleaning step, and recovered in a given recovery part. Residual charges on the surface of the photoreceptor after cleaning are removed by a charge removing apparatus in the charge removing step for the next image formation.
Examples of the developer which develops an electrostatic latent image on a surface of a photoreceptor include one-component developers consisting of a toner and two-component developers comprising a toner and a carrier.
For example, in Japanese Unexamined Patent Publication JP-A 2006-292820 is disclosed a toner containing a resin comprising an epoxy resin having grafted thereto a rosin, and a binder resin in order to realize low temperature fixing that can achieve energy saving in such an image forming apparatus.
Furthermore, in JP-A 2008-20631 is disclosed a toner containing a polyester resin containing a purified rosin, and a graft polymer comprising a polyolefin resin having grafted thereto a vinyl resin comprising styrene or an acryl monomer.
However, the toner disclosed in JP-A 2006-292820 does not contain a flexible component in a resin, and therefore has the problem that dispersibility of a release agent is decreased. Where the dispersibility of a release agent is decreased, the release agent is liable to be exposed on a surface of toner particles, and toner particles are liable to become massed together at high temperature.
The toner disclosed in JP-A 2008-20631 is that dispersibility of a pigment and a release agent can be improved by containing a graft copolymer in a resin.
However, reactivity between a polyolefin resin and a vinyl resin is low. Therefore, a sufficient amount of the graft polymer cannot be contained in the toner, resulting in insufficient dispersibility of the pigment and the release agent in the toner. As a result, there are the problems that color reproducibility is decreased, and toner particles are liable to become massed together at high temperature.